Hi Chris, Any thoughts or suggestions on this? Regards, Subhash > -----Original Message----- > From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc- > owner@xxxxxxxxxxxxxxx] On Behalf Of Subhash Jadavani > Sent: Thursday, April 05, 2012 11:16 AM > To: linux-mmc@xxxxxxxxxxxxxxx > Cc: linux-arm-msm@xxxxxxxxxxxxxxx > Subject: Changing the way MMC block request ends > > Hi, > > For completing any block request, MMC block driver is calling: > spin_lock_irq(queue-lock) > __blk_end_request() > spin_unlock_irq(queue-lock) > > But if we analyze the sources of latency in kernel using ftrace, > __blk_end_request() function seems to hold a spinlock with interrupts > disabled for up to 6.5 ms sometimes. __blk_end_request() calls couple of > functions and ftrace output shows that blk_update_bidi_request() function > is almost taking 6ms. So I was wondering why can't we use the > blk_end_request() rather than __blk_end_request(). Both function does the > same thing except blk_end_request() doesn't take up the spinlock while > calling the blk_update_bidi_request(). Is there any race condition which > could occur if we call blk_update_bidi_request() without queue lock? > > I looked into blk_update_bidi_request() function and it mainly updates bio's > of a request and doesn't look to do any manipulation with request queue > structure of block device. There are many block drivers (SCSI, IDE etc .) other > than MMC uses blk_end_request() rather than __blk_end_request(). Was > there any special reason we are using __blk_end_request() in MMC block > driver? If there is no specific reason, I would like to post a patch which would > make MMC driver to use blk_end_request(). > > Let me know your thoughts on this. > > Regards, > Subhash > > -- > Sent by a consultant of the Qualcomm Innovation Center, Inc. > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora > Forum. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the > body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at > http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
